Fuse plug



March 9, 1937. LUDW'IG I 2,073,160

FUSE PLUG Filed May 17, 1934 /7 v .& a,

INVENTOR. 1. 0111 5 udwly ATTORNEY Patented Mar. 9, 1937 UNITED STA PATENT OFFICE FUSE PLUG poration of New York Appiication May 17, 1934, Serial No. 726,081

4 Claims.

My invention relates to fuse plugs of the type having an opening covered with transparent material through which the interior of the plug may be observed and is a further improvement on Patent No. 1,776,685, granted to me on September 23, 1930.

The invention has for its main object to provide means within such a fuse plug which will positively indicate when the fuse is blown. Another object is to use these means for indicating the capacity of the fuse. A further object is to so construct these means that, while greatly improving the fuse, they will add but slightly to its manufacturing cost. 15 This and other objects and advantages will be readily understood from the following description and from the accompanying drawing of preferred embodiments of the invention in which, however, modifications may be made without departing from the scope of appended claims. In the drawing Fig. 1 is a top view of a fuse plug containing my invention,

Fig. 2 a cross-sectional side view of Fig. 1,

25 Fig. 3 another, but fragmental, cross-sectional side view,

Fig. 4 a plan view of one of the means used for indicating the blowing of a fuse, Fig. 5 a side view of same, and 30 Fig. 6 a plan view of modification.

Referring now to all the views, simultaneously, it is the ordinary porcelain body of a fuse plug, H the threaded metal ferrule, E2 the cap, I3 the opening in the cap through which the in- 35 terior recess i i of the body may be observed, and I5 the transparent mica disk covering this opening.

The invention consists in bringing the fusible metal strip l5 right up to the mica disk and 40 provides an indicating disk ii, in which slits l8 and i9 are made so that a tongue 29 is formed. The tongue is placed under the upper part of the fusible metal strip and the whole indicating disk, including the free end of the tongue, is 45 clamped between the mica disk and the body member when the cap is secured in its place.

It will thus be seen from Fig. 1, that the weakened part of the fusible strip is exposed on top of the indicating disk and in contact with the 50 mica. The indicating disk may be made of any non-conducting material and I have found that ordinary, stiff paper serves very well. When the fuse is blown, the gases are temporarily retained between the mica disk and the indicating disk. 55 This causes the gases to blacken the mica to such an extent that the whole indicating disk is obscured from view, but still does not rupture the mica.

By stamping the indicating disk with some symbol, as for example O-K, anyone may observe that the fuse has not been blown and is in serviceable condition. The blowing of the fuse will obliterate these indicating marks as well as the indicating disk itself. To facilitate the insertion of the tongue 20 under the fusible metal strip, the end of the tongue extends slight- 1y beyond the circumference of the disk and is pointed as shown at 2|.

In Fig. 6 instead of employing a disk, a strip 22 of non-conducting material is passed underheath the strip and secured between the body member and the mica disk as in the former case. This embodiment will cause sufficient blackening of the strip to obliterate the indicating marks. The strip may also be made of material so fragile that it will be destroyed when the fuse is blown.

The indicating disk may be made in various colors to designate the capacity of the fuse, or its capacity may be printed directly on the disk 25 as shown in Fig. 4.

From the foregoing it will be seen that this improved fuse effectively serves the purpose for which intended, and that it is extremely simple and inexpensive to manufacture.

Having described my invention and its object, what I claim is new and wish to protect by Letters Patent is:

1. In a fuse plug, an insulating body member having an interior recess covered with a transparent disk secured to the body member, a metal ferrule secured on the outside of said body member, a metal contact secured in the bottom of the body member, a fusible metal strip contained in the recess and connecting the ferrule with the center contact, a part of the fusible metal strip bent up adjacent to the transparent disk, an indicator disk of non-conducting material, having a tongue formed by two slits extending from the edge of the disk to a short distance beyond its center, the tongue inserted under the bent-up part of the fusible metal strip, and the indicator disk together with the free end of the tongue secured between the transparent disk and the body member so that a shallow chamber is formed in which the exposed part of the fusible strip is housed and from which gases from the blowing of the fuse may be released into the interior recess through the said slits.

2. In a fuse plug, an insulating body member having an interior recess covered with a transparent disk secured to the body member, a metal ferrule secured on the outside of said body member, a metal contact secured in the bottom of the body member, a fusible metal strip contained in the recess and connecting the ferrule with the center contact, a part of the fusible metal strip bent up adjacent to the transparent disk, an indicator disk of non-conducting material having symbols imprinted thereon indicative of the condition of the fuse, having a tongue formed by two slits extending from the edge of the disk to a short distance beyond its center, the tongue inserted under the bent-up part of the fusible metal strip, and the indicator disk together with the free end of the tongue secured between the transparent disk and the body member so that a shallow chamber is formed in which the exposed part of the fusible strip is housed and from which gases from the blowing of the fuse may be released into the interior recess through the said slits.

3. In a fuse plug, an insulating body member having an interior recess covered with a transparent disk secured to the body member, a metal ferrule secured on the outside of said body member, a metal contact secured in the bottom of the body member, a fusible metal strip contained in the recess and connecting the ferrule with the center contact, a part of the fusible metal strip bent up adjacent to the transparent disk, an indicator disk of non-conducting material, having a tongue formed by two slits extending from the edge of the disk to a short distance beyond its center, the tongue inserted under the bent-up part of the fusible metal strip, the indicator disk together with the free end of the tongue secured between the transparent disk and the body member so that a shallow chamber is formed in which the exposed part of the fusible strip is housed and from which gases from the blowing of the fuse may be released into the interior recess through the said slits, and the indicator disk provided with means for indicating the capacity of the fuse.

4. In a fuse plug, an insulating body member having an interior recess covered with a transparent disk secured to the body member, a metal ferrule secured on the outside of said body member, a metal contact secured in the bottom of the body member, a fusible metal strip contained in the recess and connecting the ferrule with the center contact, a part of the fusible metal strip bent up adjacent to the transparent disk, an indicator disk of non-conducting material having a tongue formed by two slits extending from the edge of the disk to a short distance beyond its center, the tongue inserted under the bent-up part of the fusible metal strip, the indicator disk together with the free end of the tongue secured between the transparent disk and the body member so that a shallow chamber is formed in which the exposed part of the fusible strip is housed; and the end of the tongue extending beyond the periphery of the disk to facilitate the insertion of the tongue under the fusible strip.

LOUIS LUDWIG. 

